1. Field of the Invention
The present invention relates to an electronic weighing apparatus. More specifically, the present invention relates to an electronic weighing apparatus for converting a displacement amount of a displacement plate caused by the weight of an article into a train of pulses, counting the number of pulses for generating a digital value of the weight of the article, and displaying the weight value in a digital manner.
2. Description of the Prior Art
Of late, an electric or electronic weighing apparatus for weighing the weight of a human body and for displaying the weight value in a digital manner has been proposed and put into practical use in place of a conventional mechanical body weight weighing apparatus. Such electronic weighing apparatus requires a power source such as a battery to engergize various electronic circuits and a digital display. Although an electronic weighing apparatus for other applications may be energized by a commercial alternating current power supply line, it is most desired that a body weight weighing apparatus employs a battery as a power supply from the standpoint of safety, in consideration of a possibility that such body weight weighing apparatus is often used in a bathroom of a relatively high humidity. It is required that such electronic weighing apparatus using a battery is energized with the least possible power consumption, whereby measurement of a constant precision is ensured for a longer period of time. To that end, it has been a common practice that such an electronic weighing apparatus using a battery as a power supply is structured to comprise a human operable switch, such as a foot switch, so that the switch is turned on before measurement and is turned off after measurement. However, such operation of a human operable switch before and after measurement is tiresome. In order to eliminate such tiresomeness, therefore, one might think of an alternative approach of providing a limit switch, so that the same is turned on only if and when a human stands on an electronic weighing apparatus and is turned off when he gets off. On the other hand, in case of such an electronic weighing apparatus structured to generate a train of pulses in association with a displacement of a displacement plate and to count the number of pulses to provide the weight value data, it is required that a power supply has been turned on at least before the start of a weighing operation. Nevertheless, in the case where a limit switch is employed for energization responsive to a load, it is extremely difficult or hardly possible to make the timing of the start of a weighing operation coincide with the timing when the limit switch is turned on, with the result that an accurate weighing operation is exremely difficult or is hardly possible. Even if an electronic weighing apparatus is implemented using such a limit switch, it is required to use a switch mechanism of a very high precision, which is usually expensive. Nevertheless, it is extremely difficult or hardly possible to ensure for a long period of time that the apparatus operates such that the start of a weighing operation and the start of the power supply occur at the same time.